An important purpose of many communication networks is delivering data for video and/or audio content to premises of network subscribers. This content may be from programming services that originate from broadcast television networks (e.g., ABC, CBS, NBC), programming services from other commercial providers (e.g., HBO, ESPN), programming services that retransmit content from local over-the-air television stations, video on demand (VOD) services, etc. Although sometimes called “cable television” (CATV), such content delivery may actually involve various types of media and access network technologies, such as fiber optic and/or wireless networks.
The audio and video content that a user associates with a particular CATV “channel” or other programming service is often received at a gateway, Set Top Terminal (STT) or other subscriber device as a collection of separate multicast or unicast digital data streams. Multicast content such as conventional CATV programming may be provided (or at least available) to large numbers of subscribers simultaneously. Typically, many subscriber devices in an access network may be simultaneously receiving numerous multicast data streams in different frequency bands and/or as separate MPEG (Motion Picture Expert Group) transport streams within a particular frequency band. When a user wishes to watch a particular channel, a subscriber device at the user's premises identifies the appropriate data stream(s) for the desired channel. Data from those streams is then demodulated, decoded and otherwise processed so that audio and/or video output can be generated on a television or other end device. Unicast content data (e.g., for VOD programming) is normally addressed to a single subscriber device in response to a specific request from that device.
For a variety of reasons, it is desirable to transmit both unicast and multicast content data to subscriber devices in Internet Protocol (IP) packets. However, implementing end-to-end multicast IP content delivery poses challenges in some types of existing access networks. As but one example, some network operators deliver programming content data, provide high speed data communication and voice over IP (VoIP) telephony, and facilitate other types of communications over networks, such as wireless, fiber optic or cable networks. Once such network, for example, is a hybrid fiber coaxial (HFC) access network that complies with one or more Data Over Cable System Interface Specification (DOCSIS) standards promulgated by Cable Television Laboratories, Inc. (CableLabs®) of Louisville, Colo. In a DOCSIS-compliant access network, data is transmitted to subscribers via a device known as a Cable Modem Termination System (CMTS). However, routing numerous multicast and unicast IP content data streams through a CMTS could be costly and present scaling problems. A possible alternative is to DOCSIS encapsulate multicast content data at a source and deliver that DOCSIS encapsulated data directly to an Edge Quadrature Amplitude Modulation (EQAM) device in an access network. However, this approach requires a content source or other device to have DOCSIS encapsulation capability. This approach also fails to leverage benefits available in a multicast IP content distribution system.